Transmission detector for a window body in particular the windshield of a motor vehicle and a cleaning device for a viewing area of a window body

ABSTRACT

A transmission detector ( 1 ) for a window body ( 2 ), in particular the windshield of a motor vehicle, has an optical sensor device ( 4, 6, 7, 17 ) which includes an imaging system ( 4, 7 ) and a position-sensitive optical detector ( 6 ). In addition, the transmission detector ( 1 ) has an analyzing system ( 10 ) for the image data recorded by the optical detector ( 6 ). The imaging system ( 4, 7 ) is designed such that sections of a surface of the window body ( 2 ) whose distance to one another is comparable to the size of the free aperture of the window body ( 2 ) are projected on the optical detector ( 6 ). This allows for a precise allocation of the variables affecting the transmission of the window body ( 2 ). A cleaning system for a viewing area of a window body ( 2 ) being equipped with this transmission detector ( 1 ) also has a cleaning device ( 28, 29, 31, 32 ) which is controlled by the analyzing system ( 10 ). Such a cleaning system may be triggered as needed.

[0001] The present invention relates to a transmission detector for awindow body, in particular the windshield of a motor vehicle accordingto the definition of the species in Claim 1, and a cleaning device for aviewing area of a window body according to the definition of the speciesin Claim 17.

[0002] Such a transmission detector and such a cleaning device are knownfrom German Patent Application 197 49 331 A1. A sensor array, situatedon the base of an interior mirror of a motor vehicle, parallel to theexterior surface of its windshield, operates there as aposition-sensitive optical detector for detecting objects, e.g., raindroplets on the exterior of the windshield. The sensor array covers onlya small section of the windshield. Influencing factors on thetransmission of the windshield which do not evenly affect the entirewindshield surface may thus be detected either with relatively greatuncertainty or not at all.

[0003] A further transmission detector and a cleaning device equippedwith it are known from German Patent Application 199 43 887 A1. Here,the radiation, emitted from a relatively small section of a windshieldof a motor vehicle, is utilized with the aid of a position-insensitivedetector for transmission detection. In addition to the disadvantagesmentioned, due to the coverage of only a small section of the windowbody, additional limits arise here due to the fact that, by using such atransmission detector, it cannot be determined which type of effect,e.g., which type of object on the windshield, has triggered thetransmission change of the window body.

[0004] It is thus the first object of the present invention to refine atransmission detector according to the definition of the species inClaim 1 in such a way that transmission effects which are unevenlyspread across the window body may also be reliably detected.

[0005] According to the present invention, this object is achieved by atransmission detector having the features provided in Claim 1.

[0006] By detecting sections of the surface of the window body, whichare distanced from one another by an amount on the order of magnitude ofthe free aperture, it may be determined, by using the transmissiondetector according to the present invention, whether or not atransmission effect, acting evenly on the window body, exists. If aneven transmission effect exists, e.g., due to rain droplets or an evendust or pollen layer on the window body, then the sections that aredistanced from one another are affected in the same way. As a rule, thisis not the case when an uneven transmission effect exists, e.g., anuneven soiling of the window body. Where applicable, the transmissiondetector may be part of an optical detection device, e.g., for theidentification of driving lanes, resulting in improved cost efficiencydue to the joint utilization of components.

[0007] A sensor array according to Claim 2 has a high positionalresolution. This improves the precision of the transmission detector indetermining the type of transmission effect of the window body.

[0008] A CCD (“charge coupled device”) array according to Claim 3 ishighly light-sensitive and is available in a compact design.

[0009] Sections of the surface of the window body which are fartherdistanced from one another may also be imaged with little optical effortby using a wide-angle lens according to Claim 4. If increasedrequirements must be taken into account, e.g., due to the shape of thewindow body or to the condition that the entire surface of the windowbody must be imaged if possible, an imaging system having a plurality ofoptical components may be used.

[0010] By using an aperture according to Claim 5, the area of the windowbody detected by the transmission detector may be adapted so that, forexample, a predefined transmission measuring program for determining thetransmission effect may be run. In addition, a standard transmissiondetector may be adapted to a plurality of differently dimensioned windowbodies. Exposure control of the optical sensor device may also beimplemented by using an aperture.

[0011] A controllable aperture opening according to Claim 6 ensures anautomated selection of the sections of the surface of the window body tobe imaged.

[0012] By using an actuator according to Claim 7, an area of the surfaceof the window body to be imaged may be selected as a function of ananalysis result of the transmission detector. More complicatedtransmission measuring programs may also be implemented in an automatedfashion, in which an additional area or several additional areas areselected and measured as a function of the analysis result of thetransmission measurement of a certain area. This may take place on thebasis of the initially measured area if, for example, the type and thedistribution of objects on the window body, affecting the transmission,are only known inaccurately or not yet at all.

[0013] Several apertures according to Claim 8 also facilitate theselection of complicated, i.e., irregularly shaped, sections of thesurface of the window body to be imaged.

[0014] A radiation source according to Claim 9 allows transmissiondetection even when no daylight or other external light is available.

[0015] IR radiation according to Claim 10 is perceived as undisturbingto the user. Moreover, current optical detectors are particularlysensitive in certain IR wavelength ranges.

[0016] Blurred imaged sections of the surface of the window body mayalso be analyzed by using analyzing systems according to Claims 11through 13. The dependency of the contrast, the Fourier components andthe auto-correlation function on further defined parameters accessibleto the measurement offer a measured variable which makes an adequatelyprecise conclusion on the type of transmission effect possible.

[0017] A comparator according to Claim 14 makes a relatively inexpensiveanalysis of the optical image data possible.

[0018] A refinement in determining the transmission effect is achievableby using a comparator according to Claim 15.

[0019] It has been found that a neural network according to Claim 16 isparticularly suitable for implementing a comparator including dynamicadjustment of the reference values.

[0020] A further object of the present invention is to provide acleaning device of the type mentioned earlier, in which the improvedpossibilities of detecting a transmission effect by using thetransmission detector are utilized.

[0021] This object is achieved according to the present invention byusing a cleaning system having the features according to Claim 17.

[0022] The cleaning device in such a cleaning system is only to beactivated if this is actually necessary due to transmission effects onthe window body which are removable by cleaning. This improves theefficiency of the cleaning system.

[0023] A window wiper body according to Claim 18 is a cleaninginstrument that is inexpensive and sufficient in its cleaning effect.

[0024] A window washing device according to Claim 19 results in animproved cleaning effect.

[0025] In a cleaning system according to Claim 20, the transmissiondetection takes place where the removal of disturbing transmissioneffects is most important to the user.

[0026] Disturbing transmission effects, which are not detected, areessentially eliminated by using a cleaning system according to Claim 21.

[0027] The danger of false activation of the cleaning device isminimized by controlling the cleaning device according to Claim 22.

[0028] Exemplary embodiments of the present invention are explained ingreater detail on the basis of the drawing.

[0029]FIG. 1 shows a vertical section through a passenger car in thearea of a windshield, parallel to the longitudinal axis of the passengercar;

[0030]FIG. 2 shows an enlarged detail from FIG. 1;

[0031]FIGS. 3 and 4 show frontal views of the windshields of twopassenger cars including cleaning systems having cleaning devices forthe windshield; and

[0032]FIG. 5 shows a schematic block diagram of the cleaning system.

[0033] A transmission detector, referenced in the drawing with number 1,is used for detecting foreign substances on a windshield 2 of apassenger car, e.g., rain droplets, dust particles, pollen, or localsoiling such as insect residues. Transmission detector 1 is part of acleaning system for windshield 2. Windshield 2 is depicted in FIG. 1 ina vertical section along the longitudinal axis of the passenger carbetween roof 3 of the passenger car and a body area 35 connected to thelower area of windshield 2.

[0034] Transmission detector 1 is mounted in a housing and situated onthe roof liner of the passenger car in the transition area between theupper end area of windshield 2 and roof 3 of the passenger car.

[0035] Transmission detector 1 covers the outside surface of windshield2, with the help of a wide-angle lens 4. As a function of the depth offield of wide-angle lens 4, since windshield 2 is inclined toward theoptical axis of wide-angle lens 4, the entire external surface ofwindshield 2 is not imaged but an image section 5 in the form of a stripshaped as a semicircle is sharply projected on the photosensitive screenof a video array 6. A CCD array may be used as video array 6. In FIG. 3,showing a view of the passenger car in the area of windshield 2 from thefront, image section 5 is highlighted by a rhomboidal hatch. Referencesections 8 of the external surface of windshield 2 which are alsodetectable by transmission detector 1 are depicted by a quadratic hatchin FIG. 3. The overall area of windshield 2, detectable by video array6, which is composed of image section 5 and reference sections 8 coversa surface area of windshield 2 which is comparable to the entire fieldof vision, i.e., the free aperture, of windshield 2.

[0036] In order to meet increased imaging requirements, an imagingsystem may also be utilized as an alternative to a wide-angle lens 4.

[0037] An aperture 7, which makes it possible to select the section ofwindshield 2 to be detected by video array 6, is situated in the imagingbeam path (imaging beams 9, see FIGS. 1 and 2) between wide-angle lens 4and video array 6. The opening of aperture 7 may be preset by themanufacturer or may be readjusted during operation of transmissiondetector 1 by using an actuator (not shown, see FIG. 5).

[0038] It is conceivable that a device for decoupling imaging beams 9from windshield 2 is inserted between wide-angle lens 4 and the imagingsystem.

[0039] Video array 6 communicates via signals with analyzing system 10having an integrated control unit 11 which controls the cleaningcomponents for windshield 2 yet to be described.

[0040] The internal design of analyzing system 10 is made clear in theblock diagram of FIG. 5, which schematically illustrates the opticalcomponents of transmission detector 1.

[0041] Video array 6 communicates with an exposure controller 13 ofanalyzing system 10 via data line 12. The analyzing system is connectedto an actuator 15, which is coupled to aperture 7 via a control lead 14.Furthermore, exposure controller 13 is connected to an IR transmittervia a control lead 16.

[0042] Video array 6 is connected to an analyzing device 19 of analyzingsystem 10 via an additional data line 18. The analyzing devicecommunicates via a data line 20 with a comparator 21 which in turncommunicates with control unit 11 of analyzing system 10 via a signalline 22.

[0043] Control unit 11 is connected to two windshield wiper motors 24,25 (see FIG. 3) via a control lead 23, the motors being coupled withwiper arms 28, 29 either via rods 26, 27 or directly via the outputs ofthe windshield wiper motors.

[0044] Control unit 11 of analyzing system 10 is connected to twowindshield washer units 31, 32 (see FIG. 3) for windshield 2 via acontrol lead 30. Spray areas 33, 34 of windshield washer units 31, 32are indicated in FIG. 3 with dashed lines.

[0045]FIGS. 3 and 4 show two alternative exemplary embodiments ofcleaning systems for windshield 2 which differ in the areas of theexternal surface of windshield 2 reached by wiper arms 28, 29.

[0046] The same components which have been explained with reference toFIG. 3 are labeled with the same reference numbers in FIG. 4 and are notdiscussed again in greater detail.

[0047] In the wiper configuration according to FIG. 4, wiper arms 28, 29reach a larger area of windshield 2 than is the case in the wiperconfiguration according to FIG. 3. Reference sections 8, detected bytransmission detector 1, are also similarly enlarged.

[0048] The cleaning system works as follows:

[0049] Via aperture 7 and wide-angle lens 4, video array 6 records imagesection 5 and reference sections 8 as a function of the opening ofaperture 7. Objects on windshield 2 are sharply imaged within imagesection 5, while objects in reference sections 8 are detected in ablurred form by video array 6. The sharply imaged objects are detectedwith the aid of an analysis of the measured intensity distribution whichis yet to be described. The objects, which lie outside the depth offield area of image section 5, i.e., in reference sections 8, arelikewise detected based upon the measured intensity distribution bymeasuring the blur of imaged contours. This blur depends on whetherwindshield 2 is affected in its transmission by, e.g., rain droplets(defocusing) or by ice or dust (dispersion).

[0050] The presence of such interfering objects appears in image section5 through sharply displayed details in the image, i.e., in an intensityvariation over relatively small image sections. In many cases, the typeof intensity variation is intrinsic for the type of soiling. Therefore,the type of soiling may be identified by a comparison with referencedispersions yet to be described.

[0051] The image data recorded by video array 6 are initiallytransmitted to exposure controller 13 via data line 12. Based upon acomparison with an exposure setpoint value, it is determined therewhether the illumination of windshield 2 is sufficient for transmissiondetection, and whether a section specification for the section ofwindshield 2 to be detected is fulfilled.

[0052] If the exposure setpoint value is not met, then IR transmitter17, which illuminates windshield 2 for transmission detection, isswitched on via control lead 16. If the section specification for thesection of windshield 2 to be detected is not fulfilled, then actuator15 is triggered via control lead 14 and the section specification forthe section of windshield 2 to be detected is adjusted via the openingof aperture 7.

[0053] When it is ensured that the setpoint specifications discussedhave been met, then the image data recorded by video array 6 istransmitted to analyzing device 19 via data line 18. The analysis of theintensity distribution detected is then performed by analyzing device 19in cooperation with comparator 21. A number of methods from digitalimage processing are available for performing this analysis; one methodwhich is based upon the analysis of a contrast spectrum is described asan example:

[0054] A multi-scale analysis for receiving the contrast spectrum isinitially performed, in which the recorded image is decomposed intoseveral images having decreasing resolution by repeated use of asmoothing operation. A global contrast measurement is calculated at eachresolution level, e.g., the standard deviation of the intensity valuesdetected. The contrast measure, plotted against the resolution, formsthe contrast spectrum of the image recorded by video array 6. Ifwindshield 2 is scratch-free and free of objects, only blurred objectsfrom farther away are imaged. Thus contrasts appear in the contrastspectrum only at low resolutions. If, however, there are objects inimage section 5 of windshield 2, then fine details are also imaged. Inthis case there are also contrasts in the contrast spectrum at higherresolutions. The fact that, contrary to sharp images, the contrast inblurred images declines more steeply with increasing resolution than insharp images, is utilized for blurred reference sections 8, since finedetails are more affected by blurred imaging than rough image features.The downward slope of the contrast spectrum over the resolution istherefore a measurement for the blurriness of the image.

[0055] The contrast spectrum determined in analyzing device 19 istransmitted to comparator 21 via lead 20 and is compared there withstored reference contrast spectra. Different types of visual obstructionare distinguished here based upon their similarity to certain referencedistributions. An even dust layer typically having the same granularsize results in an isolated peak in the contrast spectrum, while raindroplets which differ in size show a wider contrast distribution.

[0056] Based upon the result of the comparison in comparator 21, thelatter either controls windshield wiper motors 24, 25 via control lead23 or it controls windshield washer units 31, 32 via control lead 30when such visually obstructing objects are present.

[0057] If rain droplets are identified by the comparison in comparator21, then only windshield wiper motors 24, 25 are triggered for example.If the presence of a dust or pollen layer on windshield 2 is identified,then both windshield washer units 31, 32 and windshield wiper motors 24,25 are activated. If local soiling is present, then the activation ofonly one windshield wiper motor 24 or 25 and/or one windshield washerunit 31 or 32 is possibly sufficient. Depending on the type of visualobstruction on the window, i.e., type, distribution, and intensity ofsoiling, rain intensity, rain droplet frequency, etc., one or bothwindshield wiper motors may be operated or triggered using differentwiping speeds. If icing on the windshield is identified it may beadvisable, in particular in a parked vehicle, to initially only activatethe washer unit in order to remove the ice using the antifreeze in thewindshield washer water. During defrosting of the ice layer and thecorresponding transmission change, the windshield wiper motors may thenbe activated. This control method contributes to the protection of thewiper blades.

[0058] The reference contrast spectra and reference distributions may beobtained from images of video array 6 which were recorded immediatelyafter a wiper or washer operation. Using these reference distributions,a decision may be made about initializing a subsequent wiper or washeroperation.

[0059] Alternatively to contrast measuring, a measure of the intensityvariation of the image recorded by video array 6 may also be determinedusing other reference variables.

[0060] An example of such a reference variable is an auto-correlationfunction over the pixel distance of video array 6. Since only backgroundobjects are displayed, all displayed objects appear highly blurred atunobstructed view, i.e., the auto-correlation function of the imagedrops only slowly over the distance. If, however, there are objects onthe windshield then the image varies on much smaller distances so thatits auto-correlation function drops much faster.

[0061] A further possibility for a reference variable is an at leasttwo-dimensional Fourier transform. In the Fourier spectrum (amplitudeover the spatial frequency) a blurred image appears due to the fact thatthe amplitude of the high spatial frequencies, which represent the finerimage details, is highly attenuated compared to a sharp image.

[0062] Finally, it is also possible to provide an indirectclassification approach in which the reference variables are generatedby an appropriate analyzing device, e.g., a polynomial classifier or aneural network, by presenting a large number of exemplary images or aplurality of sets of analyzed image data, the analyzing device beingtrained to differentiate between sharp images of objects and images withblurred objects by analyzing the classification results.

[0063] Instead of an aperture 7, a plurality of apertures may also beutilized with which it is possible to finely adjust the area ofwindshield 2 to be detected by video array 6.

[0064] Control unit 11 may be designed such that windshield wiper motors24, 25 and windshield washer units 31, 32 may only be triggered bycomparator 21 if windshield wiper motors 24, 25 and windshield washerunits 31, 32 have been first manually triggered by the user. Thisprevents an erroneous initial operation in the event of wrong detection.Windshield wiper motors 24, 25, and windshield washer units 31, 32 mayalso be triggered as a function of the driver seat occupancy or theoperational status of the vehicle (vehicle is parked/engineidles/vehicle moves).

What is claimed is:
 1. A transmission detector for a window body, inparticular the windshield of a motor vehicle, comprising a) an opticalsensor device including an imaging system and a position-sensitiveoptical detector, and b) an analyzing system for the image data recordedby the optical detector, wherein c) the imaging system (4, 7) isdesigned such that sections (5, 8) of a surface of the window body (2),whose maximum distance to one another is comparable to the free apertureof the window body (2), are projected on the optical detector (6). 2.The transmission detector as recited in claim 1, wherein theposition-sensitive optical detector includes a sensor array (6).
 3. Thetransmission detector as recited in claim 2, wherein the sensor array(6) is a CCD array.
 4. The transmission detector as recited in one ofthe preceding claims, wherein the imaging system (4, 7) includes awide-angle lens.
 5. The transmission detector as recited in one of thepreceding claims, wherein the optical sensor device (4, 6, 7, 17) has atleast one aperture (7) via which a selection of the sections (5, 8) tobe imaged takes place.
 6. The transmission detector as recited in claim5, wherein at least one actuator (15) is provided for the control of theaperture opening.
 7. The transmission detector as recited in claim 6,wherein the actuator (15) communicates with the analyzing system (10)via a signal link (14).
 8. The transmission detector as recited in oneof claims 1 through 7, wherein the optical sensor device (4, 6, 7, 17)has a plurality of apertures.
 9. The transmission detector as recited inone of the preceding claims, wherein the optical sensor device (4, 6, 7,17) includes a radiation source (17) for illuminating the sections (5,8) to be imaged.
 10. The transmission detector as recited in claim 9,wherein the radiation source (17) emits IR radiation.
 11. Thetransmission detector as recited in one of the preceding claims, whereinthe analyzing system (10) is designed such that a contrast analysis ofthe intensity distribution of the imaged sections (5, 8) is performedbased upon the image data recorded by the optical detector (6).
 12. Thetransmission detector as recited in one of claims 1 through 10, whereinthe analyzing system (10) is designed such that a Fourier analysis ofthe intensity distribution of the imaged sections (5, 8) is performedbased upon the image data recorded by the optical detector (6).
 13. Thetransmission detector as recited in one of claims 1 through 10, whereinthe analyzing system (10) is designed such that an auto-correlationanalysis of the intensity distribution of the imaged sections (5, 8) isperformed based upon the image data recorded by the optical detector(6).
 14. The transmission detector as recited in one of the precedingclaims, wherein a comparator (21) is provided for comparing the analyzedimage data with reference values.
 15. The transmission detector asrecited in claim 14, wherein the comparator (21) is designed such thatthe reference values are dynamically adjusted to the results of aplurality of sets of analyzed image data.
 16. The transmission detectoras recited in claim 15, wherein the comparator (21) includes a neuralnetwork.
 17. A cleaning system for a field of vision of a window bodyhaving a cleaning device controlled by the analyzing systemcharacterized by a transmission detector (1) as recited in one of claims1 through
 16. 18. The cleaning system as recited in claim 17, whereinthe cleaning device (28, 29, 31, 32) includes a window wiper body (28,29).
 19. The cleaning system as recited in claim 17 or 18, wherein thecleaning device (28, 29, 31, 32) includes a window washing device (31,32).
 20. The cleaning system as recited in one of claims 17 through 19,wherein the imaged sections (5, 8) lie in a user's field of visionthrough the window body.
 21. The cleaning system as recited in claim 20,wherein the imaged sections (5, 8) essentially cover the field ofvision.
 22. The cleaning system as recited in one of claims 17 through21, wherein the control of the cleaning device (28, 29, 31, 32) by theanalyzing system (10) is designed such that the cleaning device (28, 29,31, 32) is controlled only after a first time activation by the user.